Chimneys and lead work are responsible for a huge share of roof leaks. Here's what to look for from the ground.
Why chimneys cause so many leaks
Anywhere a roof is interrupted by something else — a chimney, a wall, a vent — water gets a chance to find its way in. Lead flashings and mortar joints are what stop it. Both have a finite lifespan.
On older properties around Oxford, Witney and the Cotswolds, we routinely see chimney problems that have been quietly worsening for years before the homeowner spots damp on a bedroom ceiling.
1. Cracked or missing flaunching
Flaunching is the mortar that beds chimney pots into the stack top. When it cracks or breaks away, water gets into the brickwork and pots can become loose — a serious safety issue.
From the ground with binoculars, look for visible cracks, missing chunks, or pots that are no longer surrounded by tidy mortar.
2. Lifted or torn lead flashing
Lead flashing should sit flat against the chimney brickwork and tuck neatly into a chase or mortar joint. If you can see it lifting, curled at the edges, or with rippled splits, water is getting behind it.
Lifted flashing after a storm is a common emergency call-out — see our roof repairs and emergency service.
3. Failed pointing on the stack
Chimney stacks take more weather than any other part of the roof. Eroded mortar joints let water soak into the brickwork, then into the chimney breast and ceilings below.
Look for missing mortar, dark damp staining on the brickwork, or vegetation growing out of joints.
4. Leaning or moving stacks
A stack that visibly leans or has cracked rendering is a structural concern. Don't ignore it — falling masonry from a chimney is dangerous.
5. Damp patches on chimney breasts
Internal damp on the chimney breast — especially in upstairs rooms or the loft — is a strong sign that water is getting in at the stack. The cause is almost always one of the four issues above.
6. Lead valleys and abutments elsewhere on the roof
Lead isn't only on chimneys. Valleys between roof slopes and abutments where roofs meet walls also rely on lead. The same checks apply: it should be flat, neatly dressed, and well pointed.
Lead and chimney work is specialist — done badly, it leaks straight away. We handle full lead replacement, repointing, flaunching and pot work as part of our guttering and exterior roofline service. For active leaks, see our roof repairs page.
How often should chimney lead work be checked?
A visual check every couple of years is sensible, plus after any major storm. Replacement lead work typically lasts 40–60 years if installed properly.
Can I patch a leaking lead flashing with sealant?
Sealant is a temporary fix at best. Properly dressed and pointed lead is the only long-term solution.
Should an unused chimney be capped?
Yes — a vented cap keeps water out while still allowing the flue to breathe and prevent damp build-up.
Evans Roofing & Maintenance Ltd, Witney, Oxfordshire. Call 07960 482233 for a free written quote.